This invention relates to liquid chromatography equipment and, more particularly, to liquid chromatography column apparatus which preferably has a modular structure, useful in analytical semi-preparative and preparative liquid chromatography separation processes. Specifically, the invention is directed to a novel and useful method and apparatus for facilitating application of compressional force on the bed of sorbent packing material within liquid chromatography column apparatus.
High pressure liquid chromatography techniques utilize pumps which have a pressure pulsation as a delivery characteristic. This pulsation has a tendency to disturb sorbent packing material in a liquid chromatography column. In particular, a void may develop at the top or head of the column. Also, "channels" may develop at the interface of the packing material and the column wall. This deterioration is exacerbated by chemical attack, high temperatures, and other factors. In this regard, the initial packing of a column may also create discontinuities in a portion of the packing material.
On the one hand, known liquid chromatography systems, such as the liquid chromatography systems disclosed in U.S. Pat. Nos. 4,283,280 and 4,313,828, do not apply pressure to the packing material while maintaining seal integrity. On the other hand, the liquid chromatography column apparatus disclosed in the copending patent application of Carl L. Shackelford and Kenneth Rainin, entitled "Modular Liquid Chromatography Column Apparatus," Ser. No. 584,611, filed on Feb. 29, 1984, and assigned to the same assignee as this application, discloses a modular liquid chromatography column apparatus which applies pressure to the packing material while maintaining seal integrity. Pressure is applied to the packing material by tightening an axial compression nut threadably connected with a threaded column tube such that an axial compression piston axially disposed within the axial compression nut is forced against a movable bed retainer in contact with sorbent packing material contained within the tube for compressing the packing material.
The modular liquid chromatography column apparatus disclosed in the aforementioned patent application of Shackelford and Rainin, Ser. No. 584,611, filed on Feb. 29, 1984, operates effectively for compressing the packing material while maintaining seal integrity in various sizes of modular liquid chromatography column apparatus having tubes with inside diameters of approximately 21.4 millimeters or less. In the case of modular liquid chromatography column apparatus having tubes with larger inside diameters, for example, 41.4 millimeters, the surface area of the top or head of the sorbent packing material is much larger and requires significantly more force for compressing the packing material so as to eliminate undesired voids and channels than in the case of the smaller modular liquid chromatography column apparatus. In order to apply sufficient pressure for compressing the packing material, large wrenches are needed for tightening the end fittings on the tubes in a manner similar to the technique used for effecting a tight seal disclosed in U.S. Pat. Nos. 4,283,280 and 4,313,828. This eliminates the advantageous feature of being able to hand tighten the end fittings of liquid chromatography column apparatus for compressing the packing material.
A liquid chromatography system which solves the hereinabove mentioned problem would be a great advance in the field of liquid chromatography equipment.